Aequorin ribbon diagram from PDB database

Aequorin is a photoprotein isolated from luminescent jellyfish (like various Aequorea species e.g. Aequorea victoria) and a variety of other marine organisms. Image File history File links Aequorin_1EJ3. ... Image File history File links Aequorin_1EJ3. ... The Protein Data Bank (PDB) is a repository for 3-D structural data of proteins and nucleic acids. ... Luminescence is any emission of electromagnetic radiation. ... Orders Stauromedusae Coronatae Semaeostomeae - Disc jellyfish Rhizostomae Jellyfish (also called jellies or sea jellies as they are not true fish) are animals that belong to the class Scyphozoa (from Greek skyphos cup and zoon animal) which is in the Phylum Cnidaria. ... Binomial name Aequorea victoria (Murbach and Shearer, 1902) Aequorea victoria is a luminescent jellyfish found off the west coast of North America. ...

Aequorin is composed of two distinct units, the apoprotein apoaequorin, with an approximate molecular weight of 22 kDa, and the prosthetic group coelenterazine (molecular weight 472), a molecule belonging to the luciferin family. An apoprotein is a protein without its characteristic prosthetic group or metal. ... AMU redirects here, but may also refer to the Arab Maghreb Union The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic masses and molecular masses. ... A coenzyme (a. ... A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... Luciferin is a generic name for light emitting pigments found in organisms capable of bioluminescence, like fireflies, deep sea fish and microbes. ...

In the presence of molecular oxygen the two components of aequorin reconstitute spontaneously, forming the functional protein. Researchers have located a number of EF-hand type regions in the structure of Aequorin that function as binding sites for Ca²⁺ ions: when Ca²⁺ occupies such sites, the protein undergoes a conformational change and converts through oxidation its prosthetic group, coelenterazine, into excited coelenteramide and CO₂. As the excited coelenteramide relaxes to the ground state, blue light (wavelength = 469 nm) is emitted. General Name, Symbol, Number oxygen, O, 8 Chemical series Chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ... Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ... The wavelength is the distance between repeating units of a wave pattern. ...

Since the emitted light can be easily detected with a luminometer, aequorin has become a useful tool in molecular biology for the measurement of intracellular Ca²⁺ levels. Cultured cells expressing the aequorin gene can effectively synthesize aequorin: however recombinant expression only yields the apoprotein, therefore it is necessary to add coelenterazine into the culture medium of the cells to obtain a functional protein and thus use its blue light emission to measure Ca²⁺ concentration. Coelenterazine is a hydrophobic molecule, and therefore is easily taken up across plant and fungal cell walls, as well as the plasma membrane of higher eukaryotes, making aequorin suitable as a Ca²⁺ reporter (calcium in biology) in plants, fungi and mammalian cells. Molecular biology is the study of biology at a molecular level. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... Recombinant proteins are proteins that are produced by different genetically modified organisms following insertion of the relevant DNA into their genome. ... A cell wall is a more or less solid layer surrounding a cell. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... Calcium plays a vital role in the anatomy, physiology and biochemistry of organisms and of the cell, particularly in signal transduction pathways. ...

Aequorin has a number of advantages over other Ca²⁺ indicators: it has a low leakage rate from cells, lacks phenomena of intracellular compartmentalization or sequestration and it does not disrupt cell functions or embryo development. Moreover the light emitted by the oxidation of coelenterazine does not depend on any optical excitation, so problems with auto-fluorescence are eliminated.

References

• Swiss-Prot Aequorin entry
• A. Mithöfer and C. Mazars, Aequorin-based measurements of intracellular Ca²⁺ signatures in plant cells [1]